Portable radiotelephones, such as pocket-sized cellular telephones and second generation (CT2) cordless telephones are becoming increasingly more popular, especially as the size and the cost of the portable radiotelephones has been reduced. Current portable radiotelephones utilize an audible ringing signal to alert the portable radiotelephone user of an incoming call. There are, however, drawbacks to the use of an audible ringing signal. One such drawback is that when the portable radiotelephone is carried in a pocket, the audible ringing signal can become muffled, which can result in the portable radiotelephone user missing a call. Furthermore, there are many areas of public business, such as in theaters and in restaurants, where the use of devices providing an audible ringing signal are being banned, because the audible ringing signal is an annoyance to other customers at the establishment.
Tactile, or silent alerting devices have been utilized for some time in portable communication devices, such as pagers, to provide a vibratory alert signal. The tactile alerting device of choice in prior art portable communication devices has been a motor driven eccentric weight vibrator. While such motor driven eccentric weight vibrators have proved acceptable for use in some portable communication devices, they are generally unacceptable for use in current portable radiotelephones due to the increased space which is required to mount the motors. Also, most portable radiotelephones have only a very limited battery life, and the use of a motor driven eccentric weight vibrator which requires a significant current drain for operation would further reduce the operating time available for such portable radiotelephones.
What is therefore needed for use in a portable radiotelephone is a tactile alerting device which does not require any increase in space to mount the device, and furthermore does not provide a significant increase in current drain when being operated. What is further needed is a tactile alerting device which can be operated in a dual mode to provide not only a vibratory alert, but can also provide a limited frequency range voice reproduction of an audible voice message signal, thereby eliminating the need for a separate audio transducer.